Multi-objective Optimisation of Torsion Beam Structure of Driverless Vehicle Chassis for Improved Fatigue Resistance

The fatigue resistance of the torsion beam is the keyway to prolong the service life of the chassis of the driverless vehicle. The rigid-flexible coupling finite element model of the chassis is constructed using anti-fatigue algorithm. In this model, the stress time history of the torsion beam is obtained by modal stress recovery. The nominal stress method is used to analyze the fatigue life of the structure. It is known that the structure weight affects the fatigue life, so the algorithm aims at lightening the structure to realize the improved fatigue resistance of the torsional beam structure. The parametric model of torsion beam is constructed with mass and fatigue life as optimization objectives, first-order torsion mode frequency and torsion stiffness as constraints. Multi-objective particle swarm optimization (MPSO) based on the Kriging model is used to achieve improved fatigue life of the torsion beam. After optimization, the structural weight of the torsion beam is reduced by 19.20%, and the light-weight and anti-fatigue effect are better than the baseline design.

Multi-Objective Collaborative Flexibility Optimization Design of the Strengthening Layer of a Flexible Riser

Marine flexible risers are widely used in ocean oil and gas extraction, and need to withstand environment loads (wave and current) and the large offset of the floater. Therefore, the flexible riser is subjected to tension, bending and torsion loads, which are mainly resisted by the key strengthening layer. Small bending stiffness of a cross section of the strengthening layer with larger tension and torsion stiffness are required to be compliant with the ocean environment. The traditional design of the key strengthening layer is partially rigid with larger cross-sectional stiffnesses. Therefore, the innovative configurations of the strengthening layer are imperative to make sure that the flexible riser is reliable and safe during the installation and operation. The strengthening layer of the flexible riser is treated as the cylindrical shell composed of periodic unit-cell beam structures, which is a hypothetical model. The optimization design is conducted through the novel implementation of the asymptotic homogenization (NIAH) method. The multi-objective collaborative flexibility optimization formulation of cylindrical shell structure is proposed, considering the ratio of cross-sectional tensile torsion stiffness to bending stiffness of the strengthening layer as the objectives. The optimal configuration results, the helically wound structures, are obtained, which are the alternative strengthening components of flexible risers. Finally, the optimal structures are compared with the commonly used marine flexible riser, which gives a great verification of the methodology feasibility, and explains why the strengthening layer is designed as the type of helically wound structure.

Design and Theoretical Analysis of High-Static-Low-Dynamic Stiffness Torsion Vibration Isolator Based on Oblique Springs

A torsion vibration isolator composed of oblique springs with high-static-low-dynamic stiffness (HSLDS) is proposed to attenuate the transmission of torsion vibration along the shipping shaft in this paper. It is good at in low frequency vibration isolation as it can significantly reduce the resonance frequency of the system with the same load capability. Firstly, the model of HSLDS torsion vibration isolator is introduced in this paper. Secondly, the non-dimensional torsion stiffness is formulated using mechanics theory, and the HSLDS characteristic of designed torsion vibration isolator is verified. Finally, the torque transmissibility is analyzed using the Increment Harmonic Balance (IHB) method, and the effects of the system parameters on it are analyzed. The results show that the resonant frequency increases accordingly as the stiffness ratio and the excitation torque are increased. However, the peak value of the torsion transmissibility is decreased as the damper ratio increasing.

Evaluate equivalent-sectional shear modulus for laminated glass beams using in torsion tests and photogrammetry method

This paper proposes a concise concept for quantifying the shear/torsional stiffness of the laminated glass beams experimentally by introducing the Equivalent-Sectional Shear Modulus (ESSM), that is directly measured from the torque and sectional-rotation correlation with the torsion test and tailor-made photogrammetry technique. The advantage of this method is originated from the concept of measuring the overall rotation to torque response of a laminated glass beam altogether rather than the component individually. This eliminates the uncertainties of analytical approximations that are commonly adopted by most existing methods in which the composite shear/torsion stiffness is derived from its component mechanical properties. The photogrammetry technique increased the accuracy of the sectional rotation measurement by acquiring dense displacement sample points on the glass beam simultaneously. The accuracy of the photogrammetry setup and efficacy of the test design were proven by a micrometre and a monolithic glass beam test. One sample each for the polyvinyl butyral (PVB) and SentryGlas Plus (SGP) laminated glass beams were tested multiple times non-destructively to determine the ESSM. The result of the SGP laminated glass beam showed a closer agreement with the previous studies, however the result of the PVB laminated glass beam exhibited a larger difference from the previous studies. It also suggested that mechanical properties of the interlayer played an important role in the composite behaviour of the laminated glass beam. The experimental outcomes have demonstrated the proposed method is an accurate and effective technique for measuring the ESSM of laminated glass beams.

Full Scale Axial, Bending and Torsion Stiffness Tests of a Three Core HVAC Submarine Cable

Submarine, export cables behave, to some point, as long, flexible cylindrical bodies. Their mechanical performance is crucial during laying and operating processes, which depends to a large extent on their stiffness. Although theoretical methods, used to estimate cable stiffness, are currently available, it is difficult to account for the various physical mechanisms involved, such as internal friction, residual torsion and ‘relaxation’ effects. These mechanisms are expected to affect cable stiffness and should be included some way. To represent more realistically cable stiffness, full-scale tests are performed in this paper. The deviation between theoretical and experimental values appears to be significant in certain cases: hence, non-realistic values for cable stiffness would occur if the stiffness estimation relied only on the theoretical methods. Interesting results, affording an in more depth insight and allowing for a better understanding of the cable mechanical performance, are presented in this paper.

TORSIONAL STIFFNESS AS AN INFLUENCE PARAMETER ON ARCH STABILITY

Arch bridge springs can be connected to concrete abutments either by prestressing bars or by connectors. In both options, the torsional stiffness is substantially reduced, compared to the full arch cross sectional area. The influence of this lack of torsional stiffness on arch buckling is being researched, both numerically and experimentally. To reduce any residual stress during tests, wooden rods that simulate the arch were submerged in water and subsequently bent to the desired shape. Imperfections of the arch samples are measured. Two unequal concentrated loads are applied to the samples, thus simulating the effect of movable loads across half of the arch span. During loading, lateral deflections were measured until elastic buckling occurred. The simulation of more flexible rotation of the springs required replacing the cross section by thin equivalent side plates. Since all parameters have not been isolated, the results are limited yet. However, comparing the failure load of similar conditions, the reduction of torsion stiffness by 81.48% reduces the failure load by 26.3%. This indicates that total prevention of axial rotation may not be imperative for arch bridges.

Analysis of LCV Chassis for Optimizing Weight by Using FEM

Chassis is the component of an automobile that acts as the frame to support the vehicle body. This study main objective of the study reduce the overall weight of the chassis with help of FEA method. Increase the overall strength of the chassis. Calculated the stress and deformations at different loading conditions. Proposed the best suitable material for chassis design. This results are the total weight of the chassis reduce up to 37 kg. And total deformation and equivalent stress was 26.285mm and10.441mpa. The FEA Analysis Of Tata Ace Chassis design is built with low density carbon fiber (1298Kg/m3) since it is a less weight and has an excellent strength weight ratio and shows good bending and torsion stiffness comparing with other material hence FEA Analysis Of Tata Ace Chassis with carbon fiber material is a best alternative design for the light weight chassis design.

Design and optimization of electric bus monocoque structure consisting of composite materials

This paper proposes a novel design methodology for electric-bus structures by implementing the finite element method via ABAQUS™ and linear programming via MATLAB™. A monocoque sandwich-structured fiber-reinforced composite bus with a maximum driving range of 300 km is conceived using the proposed methodology. The bus-body structure is designed based on safety criteria such as vehicle registration regulations, the strength of the bus structure under various driving conditions, bending- and torsion-stiffness requirements, and the rollover testing standard of UN ECE R66. A procedure developed to systematically conduct parametric studies by varying the core and face thicknesses of the sandwich structure of each component is presented. Multivariate functions are formulated to determine the correlations of structural responses with changes in geometric parameters. Linear programming is implemented to minimize the mass of the bus structure under design constraints. The proposed monocoque bus structure meets all requirements, and its body mass is 63.3% less than the benchmark value.